The present invention generally relates to imageable articles, and their methods of manufacture and imaging, and more particularly to imageable articles that include a laser-imageable layer that is the reaction product of a metal precursor and a reactant.
Many techniques are commercially available for imparting images or information onto labels, tapes, and like articles. This includes various printing techniques such as flexography, lithography, and electrophotography.
It is also known to use a laser to impart images or information onto materials which can be imaged by laser. For example, U.S. Pat. No. 5,766,827 discloses a process for forming an image on a substrate comprising the steps of providing an imageable element comprising a film having a coating of a black metal on one surface thereof, directing radiation in an imagewise distributed pattern at said black metal layer with sufficient intensity to substantially increase the light transmissivity of the medium in the irradiated region in an imagewise distributed pattern, said element having no layers comprising a thermally activated gas-generating composition. The image comprises residual black metal on the film base, and may be used for overhead transparencies, contact negatives/positives, and the like. A preferred embodiment of the black metal layer comprises a black aluminum layer comprising from at least 19 atomic percent of oxygen to less than 58 atomic percent oxygen.
WIPO PCT publication WO/0069648 discloses a method of imaging an article comprising a metal/metal oxide imageable layer with a laser beam, to impart a color image on the article. The method includes: a) providing an article including a substrate and an imageable layer, the imageable layer comprising a metal/metal oxide layer; b) imagewise applying a laser beam to the article; and c) in the portion of the article having the laser applied thereto, imparting a color to the metal/metal oxide layer different from the color in the non-imaged portion. Preferably, the imageable layer comprises aluminum/aluminum oxide.
EP 684145 discloses a recording element that includes a metal recording layer that is on a roughened substrate, the substrate having an Ra of at least 0.2 xcexcm and containing a roughening agent at a coverage of between 0.05 and 1.0 g/m2, the roughening agent having an average particle size between 0.3 and 2.0 xcexcm (page 3, lines 1-9). With regard to the metal layer, the reference explains that possible metals for the recording layers in this invention include Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Sn, As, Sb, Bi, Se, Te. These metals can be used alone or as a mixture or alloy of at least two metals thereof. The reference explains that, due to their low melting point, Mg, Zn, In, Sn, Bi and Te are preferred, with Bi the most preferred. The metal recording layer may be applied on top of the layer containing the roughening agent by vapor deposition, sputtering, ion plating, chemical vapor deposition, electrolytic plating, or electroless plating. In the preferred case of Bi the recording layer is preferably provided by vapor deposition in vacuo (page 4, lines 46-52).
EP 980764 is a later reference by the same applicant as that of the just-discussed EP 684145 reference. The ""764 reference discloses a recording element that includes a thin metal layer and a protective layer, characterized in that the element contains hypophosphorous acid, or phosphorous acid, or a mixture of both, with bismuth being the preferred metal layer (page 3, lines 41-51). The ""764 references describes previous methods of vacuum deposition of thin bismuth layers as being complicated, cumbersome, and expensive (page 3, lines 14-15).
U.S. Pat. No. 6,066,437 discloses a film which is lettered with a laser beam comprising at least one protective film which is transparent to the laser beam, at least one opaque layer which is ablated by the laser beam, and at least one contrast-forming layer on its bottom. The ablatable layer is preferably a metallic layer and can have a color like the contrast-forming layer. The color of the metallic layer is different from the color of the contrast-forming layer. The contrast-forming layer is either applied, imprinted or varnished onto the metallic layer. The contrast-forming layer can be at least one plastic film. On a side of the contrast-forming layer facing away from the metallic layer there is an adhesive layer which is covered with a carrier material, for example, an adhesive-repellant carrier film (see Abstract). The ablatable layer is preferably a largely metallic layer since this material is preferred for working with a laser beam. With the choice of metal or metal alloy, a certain color can be imparted to the layer. According to one preferred embodiment, the metallic layer is a metal coating which has been vapor-deposited on the protective film, the metallic layer optionally containing at least one hologram. Alternatively or in addition, the metallic layer can also be colored. The metallic layer is preferably an aluminum layer which has been vapor deposited on a protective film. Alternatively to vapor deposition of the metallic layer, it is also possible to apply the metallic layer by sputtering.
WIPO International Publication Number WO 98/45827 discloses a method of recording information in a laminated structure including an intermediate layer located between a transparent layer and a non-absorbing layer. The method includes using a pulsed beam laser to ablate layers of the intermediate layer. The absorbing intermediate layer is preferable a thin metallized layer such as a thin layer of aluminum.
Electroless plating process is a known chemical process of depositing a metal or metal compound from an aqueous solution of a salt of said metal. Its applications can be found in many industries (see, e.g., xe2x80x9cElectroless Plating, Fundamentals and Applicationsxe2x80x9d, eds. G. O Mallory and J. B. Hajdu, American Electroplaters and Surface Finishers Soc., 1990). It is also widely used to metallize plastics for making the plastics conductive for electroplating or for EMI shielding applications. Deposition of a variety of metals ranging from copper and nickel to silver and gold using this process have been demonstrated. Electroless nickel plating is widely used due to the unique properties of the nickel deposits. Typically, its reaction involves the reduction of nickel ions with a reducing agent in the same solution. For example, the reduction of nickel ions with hypophosphite yields alloys of phosphorus and nickel:
Ni+2+2H2PO2xe2x88x92+2H2O - - - Ni0+2H2PO3xe2x88x92+2H++H2
H2PO2xe2x88x92+H - - - OHxe2x88x92+H2O+P (alloy with Ni)
One aspect of the present invention provides a method of imaging an article. The method of imaging an article comprises the steps of: a) providing an imageable article including: an imageable layer comprising the reaction product of a metal precursor and a reactant, where the reactant includes at least one of phosphorous and boron; a first boundary layer on a first side of the imageable layer, the first boundary layer being substantially transparent to laser radiation; and a second boundary layer on a second side of the imageable layer; b) imagewise applying a laser beam to the article through the first boundary layer; and c) in the portion of the article having the laser applied thereto, thereby decreasing the optical density of the imageable layer while maintaining the continuity of the first boundary layer. Another aspect of the present invention provides an alternative method of imaging an article. This method of imaging an article comprises the steps of: a) providing an imageable article including: an imageable layer comprising the reaction product of a metal ion and a reducing agent; a first boundary layer on a first side of the imageable layer, the first boundary layer being substantially transparent to laser radiation; and a second boundary layer on a second side of the imageable layer; b) imagewise applying a laser beam to the article through the first boundary layer; and c) in the portion of the article having the laser applied thereto, thereby decreasing the optical density of the imageable layer while maintaining the continuity of the first boundary layer.
In preferred embodiments of the above methods, step c) also maintains the continuity of the second boundary layer in the area of the article having the laser applied thereto. In other preferred embodiments of the above methods, step c) also maintains the visible appearance of the first boundary layer. In another aspect of those embodiments, step c) also maintains the visible appearance of the second boundary layer.
In other preferred embodiments of the above methods, step b) includes applying an infrared laser. In yet other preferred embodiments of the above methods, step b) includes applying a continuous wave laser. In other preferred embodiments of the above methods, step b) comprises applying no more than 3 J/cm2. In another aspect of those embodiments, step b) comprises applying no more than 500 mJ/cm2. In yet another aspect of those embodiments, step b) comprises applying no more than 300 mJ/cm2.
In other preferred embodiments of the above methods, step b) comprises applying the laser beam for between 30 nanoseconds and 30 milliseconds to each respective imaged portion. In other preferred embodiments of the above methods, the imaged portion has sufficient contrast relative to the non-imaged portion so as to create a visually perceptible image. In yet other preferred embodiments of the above methods, the imaged portion has sufficient contrast relative to the non-imaged portion so as to create a machine readable image. In another aspect of those embodiments, the machine readable image is in the form of a bar code.
In other preferred embodiments of the above methods, step a) comprises providing the imageable article in roll form. In other preferred embodiments of the above methods, step a) comprises providing the imageable article in sheet form. In yet other preferred embodiments of the above methods, the method further comprises the step of printing an image on the imageable article prior to step b). In other preferred embodiments of the above methods, the method further comprises the step of printing an image on the imageable article subsequent to step c).
Another aspect of the present invention provides a laser imageable article. The laser imageable article comprises: an imageable layer comprising the reaction product of a metal precursor and a reactant, where the reactant includes at least one of phosphorous and boron, a first boundary layer on a first side of the imageable layer, the first boundary layer being substantially transparent to laser radiation, and a second boundary layer on a second side of the imageable layer; where the imageable layer may be imaged with a laser through the first boundary layer while maintaining the continuity of the first boundary layer. Another aspect of the present invention provides an alternative laser imageable article. The laser imageable article comprises: an imageable layer comprising the reaction product of a metal ion and a reducing agent, a first boundary layer on a first side of the imageable layer, the first boundary layer being substantially transparent to laser radiation, and a second boundary layer on a second side of the imageable layer; where the imageable layer may be imaged with a laser through the first boundary layer while maintaining the continuity of the first boundary layer.
In preferred embodiments of the above laser imageable article, the first boundary layer comprises a first polymeric film. In another aspect of those embodiments, the laser imageable article further comprises an adhesive layer between the imageable layer and the first boundary layer. In another aspect of those embodiments, the first boundary layer is in direct contact with the imageable layer. In yet another aspect of those embodiments, the second boundary layer comprises an adhesive layer. In another aspect of those embodiments, the second boundary layer comprises a second polymeric film. In another aspect of those embodiments, the laser imageable article further comprises a layer of adhesive on the second boundary layer opposite the imageable layer.
In other preferred embodiments of the above imageable articles, the first boundary layer comprises an adhesive layer. In another aspect of those embodiments, the second boundary layer comprises a polymeric film. In other preferred embodiments of the above imageable articles, the metal precursor comprises one or more metal precursors selected from columns 8, 9, and 10 of the periodic table of elements. In other preferred embodiments of the above imageable articles, the imageable layer is applied by electroless plating.
In yet other preferred embodiments of the above imageable articles, the imageable layer is applied by vapor deposition or sputtering. In another aspect of those embodiments, the metal precursor comprises nickel. In other preferred embodiments of the above imageable articles, the imageable layer has a thickness of up to 400 nm. In other preferred embodiments of the above imageable articles, the imageable layer comprises from 1 to 30 mole percent phosphorus and up to 99 mole percent nickel. In yet other preferred embodiments of the above imageable articles, the imageable layer comprises from 1 to 40 mole percent boron and up to 99 mole percent nickel. In other preferred embodiments of the above imageable articles, the imageable layer has been chemically modified so as to modify its energy absorbance. In yet other preferred embodiments of the above imageable articles, the imageable article further comprises a printed image.